Methods of testing a honeycomb filter

ABSTRACT

Methods of testing a honeycomb filter for defects include the step of wetting at least one of the first end portion and the second end portion to provide at least one wetted end portion. The method further includes the step of monitoring the second end portion for fog passing through the filter.

FIELD

The present disclosure relates generally to methods of testing ahoneycomb filter and, more particularly, to methods of testing ahoneycomb filter provided with at least one wetted end portion.

BACKGROUND

Wall-flow honeycomb filters are commonly used to remove solidparticulates from fluids, such as in exhaust gas streams. FIG. 1illustrates a typical honeycomb filter 100 with an inlet end face 102for receiving the inlet gas stream, an outlet end face 104 for expellingthe outlet gas stream, and an array of generally parallel intersectingporous walls 106 extending longitudinally from the inlet end face 102 tothe outlet end face 104. The intersecting porous walls 106 define ahoneycomb network of channels 107 including a plurality of inlet cellchannels 108 and a plurality of outlet cell channels 110. The outletcell channels 110 are closed with plugs 112 where they adjoin the inletend face 102 and open where they adjoin the outlet end face 104.Oppositely, the inlet cell channels 108 are closed with porous plugs(not shown) where they adjoin the outlet end face 104 and open wherethey adjoin the inlet end face 102. Honeycomb filters 100 are typicallysecured in a compliant mat and contained in a rigid housing (not shown).Fluid directed at the inlet end face 102 of the honeycomb filter 100enters the inlet cell channels 108, flows through the interconnectingporous walls 106 and into the outlet cell channels 110, and exits thehoneycomb filter 100 at the outlet end face 104.

In a typical cell structure, each inlet channel 108 is bordered on oneor more sides by outlet cells 110, and vice versa. The inlet and outletchannels 108, 110 may have a square cross-section as shown in FIG. 1 ormay have other cell geometry, e.g., circular, rectangle, triangle,hexagon, octagon, etc. Diesel particulate filters are typically made ofceramic materials, such as cordierite, aluminum titanate, mullite orsilicon carbide. When particulates, such as soot found in exhaust gas,flow through the interconnecting porous walls 106 of the honeycombfilter 100, a portion of the particulates in the fluid flow stream isretained by the interconnecting porous walls 106. The efficiency of thehoneycomb filter 100 is related to the effectiveness of theinterconnecting porous walls 106 in filtering the particulates from thefluid. Filtration efficiencies in excess of 80% by weight of theparticulates may be achieved with honeycomb filters. However, filtrationefficiency or integrity of a honeycomb filter can be compromised byvarious defects, such as holes or cracks (such as fissures) and the likein the walls or plugs. Such defects allow the fluid to pass through thefilter without proper filtration. Thus, in the manufacture of honeycombfilters, it may be desirable to test the honeycomb filters for thepresence of such defects that may affect filtration efficiency orintegrity. Honeycombs with detected defects may be repaired, or ifirreparable, discarded.

SUMMARY

In a first aspect, a method of testing a honeycomb filter comprises thestep (I) of providing a honeycomb filter including an intermediateportion disposed between a first end portion and a second end portionalong a length of the honeycomb filter. The honeycomb filter includes ahoneycomb network of channels defined by a plurality of intersectingporous walls. The honeycomb network of channels extends along the lengthof the honeycomb filter between the first end portion and the second endportion. The method further includes the step (II) of wetting at leastone of the first end portion and the second end portion to provide atleast one wetted end portion. The wetted end portion has a higher degreeof wetness than the intermediate portion. The method further includesthe step (III) of flowing a fog with moisture droplets into thehoneycomb network of channels at the first end portion of the honeycombfilter. The method still further includes the step (IV) of monitoringthe second end portion of the honeycomb filter for moisture droplets ofthe fog exiting the honeycomb network of channels.

In one example of the first aspect, step (II) includes wetting the atleast one of the first end portion and the second end portion to a depthof at least about 5% of the length of the honeycomb filter.

In another example of the first aspect, step (II) includes wetting theat least one of the first end portion and the second end portion to adepth of at least about 20% of the length of the honeycomb filter.

In still another example of the first aspect, step (II) includes wettingthe at least one of the first end portion and the second end portion toa depth of at least about 30% of the length of the honeycomb filter.

In another example of the first aspect, step (II) includes wetting theat least one of the first end portion and the second end portion to adepth of less than about 40% of the length of the honeycomb filter.

In yet another example of the first aspect, step (II) includes wettingthe at least one of the first end portion and the second end portionwith liquid, for example water.

In a further example of the first aspect, step (II) includes dipping atleast one of the first end portion and the second end portion in liquidto provide the wetted end portion. For example step (II) can includedipping the at least one of the first end portion and the second endportion in water as the liquid to provide the wetted end portion.

In yet a further example of the first aspect, step (II) includes soakingat least one of the first end portion and the second end portion in aquantity of liquid to provide the wetted end portion. For example, step(II) includes soaking the at least one of the first end portion and thesecond end portion with a quantity of water as the quantity of liquid toprovide the wetted end portion. In another example, step (II) includesproviding the quantity of liquid as a predetermined quantity of liquidin a container, and the step of soaking draws the entire predeterminedquantity of liquid into the wetted end portion. For instance, thepredetermined quantity of liquid may be calculated to achieve wetting ofthe at least one of the first end portion and the second end portion toa predetermined depth. In another example, step (II) includes soakingsuch that liquid is drawn by capillary forces to a depth against theforce of gravity.

In a further example of the first aspect, step (II) includes wettingboth the first end portion and the second end portion to provide the atleast one wetted end portion as a first wetted end portion and a secondwetted end portion.

In still a further example of the first aspect, step (IV) includesilluminating moisture droplets of the fog exiting the honeycomb networkof channels.

The first aspect can be carried out alone or in combination with any oneor combination of examples of the first aspect discussed above.

In a second aspect, a method of testing a honeycomb filter comprises thestep (I) of providing a honeycomb filter including an intermediateportion disposed between a first end portion and a second end portionalong a length of the honeycomb filter. The honeycomb filter includeshoneycomb network of channels defined by a plurality of intersectingporous walls. The honeycomb network of channels extends along the lengthof the honeycomb filter between the first end portion and the second endportion. The method further includes the step (II) of wetting the firstend portion to a depth of from about 5% to about 40% of the length ofthe honeycomb filter to provide a first wetted end portion having ahigher degree of wetness than the intermediate portion. The methodfurther includes the step (III) of wetting the second end portion to adepth of from about 5% to about 40% of the length of the honeycombfilter to provide a second wetted end portion having a higher degree ofwetness than the intermediate portion. The method further includes thestep (IV) of flowing a fog with moisture droplets into the honeycombnetwork of channels at the first end portion of the honeycomb filter.The method still further includes the step (V) of monitoring the secondend portion of the honeycomb filter for moisture droplets of the fogexiting the honeycomb network of channels.

In one example of the second aspect, at least one of step (II) and step(III) includes wetting at least one of the first end portion and thesecond end portion with liquid, for example water.

In another example, step (V) includes illuminating moisture droplets ofthe fog exiting the honeycomb network of channels.

The second aspect may be carried out alone or in combination with anyone or combination of examples of the second aspect discussed above.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the claimedinvention are better understood when the following detailed descriptionis read with reference to the accompanying drawings, in which:

FIG. 1 is a conventional view of a honeycomb filter;

FIG. 2 is a cross sectional view of the honeycomb filter of FIG. 1 priorto wetting the second end portion of the honeycomb filter;

FIG. 3 is a cross sectional view of the honeycomb filter of FIG. 1 whilewetting the second end portion of the honeycomb filter;

FIG. 4 is a cross sectional view of the honeycomb filter of FIG. 1 afterwetting the second end portion of the honeycomb filter;

FIG. 5 is a cross sectional view of the honeycomb filter of FIG. 1 whilewetting the first end portion of the honeycomb filter;

FIG. 6 is a cross sectional view of the honeycomb filter of FIG. 1 afterwetting the first end portion of the honeycomb filter;

FIG. 7 is a test apparatus being used to test the honeycomb filter ofFIG. 6 having wetted first and second end portions;

FIG. 8 illustrates fog flow through the honeycomb filter of FIG. 6 whentesting using the test apparatus of FIG. 7;

FIG. 9 illustrates a method of wetting an outer peripheral surface ofthe honeycomb filter;

FIG. 10 is a side view of the method of wetting the outer peripheralsurface of the honeycomb filter shown in FIG. 9;

FIG. 11 illustrates fog flow through the honeycomb filter with a wettedouter peripheral surface when testing using the test apparatus of FIG.7;

FIG. 12 represents test results illustrating the effectiveness ofsaturating the outer peripheral skin of the honeycomb filter prior toconducting the testing procedure with the testing apparatus of FIG. 7;

FIG. 13 illustrates repeatability for honeycomb filters with a wettedouter peripheral skin after 30 seconds of testing;

FIG. 14 illustrates a blocking apparatus configured to reduce, such asprevent, the flow of fog through inner peripheral channels of thehoneycomb filter when conducting a testing procedure with the testingapparatus of FIG. 7;

FIG. 15 is a sectional view of the blocking apparatus in a closedorientation wherein a blocking member engages a central portion of thesecond end portion of the honeycomb filter along line 15-15 of FIG. 14;

FIG. 16 illustrates the blocking apparatus of FIG. 15 being pivoted toan open orientation;

FIG. 17 a sectional view of the blocking apparatus in a closedorientation wherein a blocking member engages a central portion of thefirst end portion of the honeycomb filter;

FIG. 18 illustrates the blocking apparatus of FIG. 17 being pivoted toan open orientation;

FIG. 19 illustrates a linear actuator being used to engage a blockingmember with a central portion of the first end of the honeycomb filter;

FIG. 20 illustrates the linear actuator of FIG. 19 being retracted to anopen orientation;

FIG. 21 illustrates an inflatable bladder being inflated to engage acentral portion of the first end of the honeycomb filter;

FIG. 22 illustrates the inflatable bladder being deflated to disengagethe central portion of the first end of the honeycomb filter; and

FIG. 23 illustrates a flow diverter being used to divert a flow of fogapproaching the first end portion of the honeycomb filter.

DETAILED DESCRIPTION

Aspects of the claimed invention will now be described more fullyhereinafter with reference to the accompanying drawings in which exampleembodiments of the claimed invention are shown. Whenever possible, thesame reference numerals are used throughout the drawings to refer to thesame or like parts. However, the claimed invention may be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein. These example embodiments are provided sothat this disclosure will be both thorough and complete, and will fullyconvey the scope of the claimed invention to those skilled in the art.

Referring now to FIGS. 2-8 illustrate one example method of testing ahoneycomb filter 100 includes the step of providing a honeycomb filter,such as the conventional honeycomb filter 100 shown in FIG. 1. Thehoneycomb filter 100 can be provided by manufacturing the honeycombfilter or portions of the honeycomb filter. In further examples, thehoneycomb filter can be provided off-the-shelf where the honeycombfilter was produced at a different location and/or purchased for latertesting. Testing the honeycomb filters may be desirable to determine ifthere are cracks or other defects in the honeycomb filter that wouldinterfere with the structural integrity, performance or othercharacteristics of the filter. Honeycomb filters that pass the testingprocedure may then be further processed to provide furthercharacteristics and/or may be mounted within a filter assembly (e.g.,diesel particulate filter) for later use.

Referring to FIG. 2, the honeycomb filter 100 includes an intermediateportion 201 disposed between a first end portion 203 and a second endportion 205 along a length “L” of the honeycomb filter 100. Thehoneycomb filter 100 includes the honeycomb network of channels 107 thatmay include a plurality of inlet cell channels 108 and a plurality ofoutlet cell channels 110. The honeycomb network of channels 107 isdefined by the plurality of intersecting porous walls 106. As shown, insome examples, the plurality of intersecting porous walls 106 may besubstantially parallel with respect to one another. As illustrate, thehoneycomb network of channels 107 can extend along the length “L” of thehoneycomb filter 100 between the first end portion 203 and the secondend portion 205.

When testing the honeycomb filter 100, it is desired to locate defectssuch as holes, cracks (such as fissures) or the like in the porous walls106 and/or the plugs 112 (e.g., porous plugs). For example, defects maybe located in the intermediate portion 201, the first end portion 203and/or the second end portion 205. For illustration purposes, a firstexample defect 207 is located in the intermediate portion 201, a secondexample defect 209 is located in the first end portion 203, and a thirdexample defect 211 is located in the second end portion 205. A nebulizeror other fog generator device may be used to help identify the defectswithin the honeycomb filter 100 by forcing fog through the filter bygenerating a pressure drop. Fog not trapped by the porous walls of thehoneycomb filter can be monitored as an indicator of a potential defectwithin the filter. Indeed, rather than being trapped by the porouswalls, the fog may freely pass through the defect, therebyshort-circuiting the desired path through the porous walls.

Defects within the first end portion 203 and the second end portion 205may be relatively easier to detect since the fluid dynamic pressuregradient between the channels that acts to push the fog through theporous walls are maximum at the first end portion 203 and the second endportion 205. In contrast, defects within the intermediate portion 201may be relatively harder to detect since the fluid dynamic pressuregradient between the channels that acts to push the fog through theporous walls may be minimized within the intermediate portion 203 of thehoneycomb filter 100.

Defects within the intermediate portion 201 may be more effectivelyidentified by a the method step of wetting at least one of the first endportion 203 and the second end portion 205 to provide at least onewetted end portion, wherein the wetted end portion has a higher degreeof wetness than the intermediate portion. Indeed, the step of wetting atleast one of the first end portion 203 and the second end portion 205can increase the sensitivity of the nebulizer or other fog generatordevice in the intermediate portion 201 of the honeycomb filter 100. Itis believed that wetting the end portions acts to at least partiallyblock the flow of air through the wetted end portion(s) by temporarilyplugging the pores via capillary forces in the vicinity of the wettedend portions(s). As such, flow through the matrix in the center third ofthe part may be increased to improve the sensitivity of the nebulizer orother fog generator device to allow more effective identification ofdefects within the intermediate portion 201 of the honeycomb filter 100.

In one example, the method can include wetting the at least one of thefirst end portion 203 and the second end portion 205. For example, thefirst end portion may be wetted to provide at least the first endportion as a wetted end portion. In another example, the second endportion may be wetted to provide at least the second end portion as awetted end portion. In still further examples both the first end portionand the second end portion may be wetted to provide a first wetted endportion and a second wetted end portion. For example, as shown in FIGS.3 and 4, the second end portion 205 may be wetted from an initial depth“D1” to a final wetted depth “D2”. As shown in FIGS. 5 and 6, the firstend portion 203 may likewise be wetted from an initial depth “D3” to afinal wetted depth “D4”.

The initial and final wetted depths may be similar or identical to oneanother in some examples. For example, the final wetted depth “D2” ofthe second end portion 205 may be similar or identical to the finalwetted depth “D4” of the first end portion 203. In alternative examples,the initial and/or final wetted depths of the first and second endportions may be different from one another. For example, the finalwetted depth “D4” of the first end portion 203 may be substantiallydifferent from the final wetted depth “D2” of the second end portion205.

In some examples, the first end portion and/or the second end portioncan be wetted to a depth of at least about 5% of the length of thehoneycomb filter. For example, the first end portion and/or the secondend portion can be wetted to a depth of at least about 20% of the lengthof the honeycomb filter. In further examples, the first end portionand/or the second end portion can be wetted to a depth of at least about30% of the length of the honeycomb filter. In still further examples,the first end portion and/or the second end portion can be wetted to adepth of at least about 40% of the length of the honeycomb filter.Increasing the depth of the wetted end portion can help further revealotherwise difficult to determine defects in the intermediate portion ofthe honeycomb filter. By way of example, FIG. 4 illustrates the defect211 of the second end portion 205 is positioned within the wetted secondend portion within the depth D2 while the defect 207 within theintermediate portion 201 remains in an unwetted intermediate portion ofthe honeycomb filter 100. Furthermore, FIG. 6 illustrates the defect 209in the first end portion 203 positioned within the wetted first endportion within the depth D4 while the defect 207 within the intermediateportion 201 still remains within the unwetted intermediate portion ofthe honeycomb filter 100. As such, testing procedures may be carriedout, as discussed below, that will enhance the visibility of the defect207 since the wetting the end portions of the honeycomb filter can actto increase the pressure differential within the intermediate portion201 during the testing procedure.

Various alternative techniques may be used to wet the first end portionand/or second end portion of the honeycomb filter. For example, wettingmay be achieve by exposing the end portion to vapor, dipping the endportion in liquid, soaking the end portion in liquid or other wettingtechniques. Vapor or liquid can comprise water vapor or liquid water(e.g., purified water). In other examples the vapor and/or liquid cancomprise glycerin, alcohol or other vapor or liquid that will not erode,corrupt or otherwise damage the honeycomb filter. In further examples,wax or other coatings may be used to substantially block air through theend portions, thereby even further increasing the pressure differentialwithin the intermediate portion where substantially all of the fog willbe forced to pass. However, such coatings (e.g., wax) may be difficultto remove and may also completely block defects within the end portions,thereby preventing simultaneous identification of defects within the endportions as well as the intermediate portion. Rather, wetting with vaporand/or liquid comprising glycerin, alcohol, water (e.g., purifiedwater), etc. can be easily removed (e.g., by evaporation) and may blockpassage of the fog through the porous walls while still permittingpassage of fog through any defects within the end portions. As such,simultaneous detection of defects within the end portions as well as theintermediate portion can be achieved.

Example techniques for wetting the second end portion 205 will now bedescribed with the understanding that such techniques may be equallycarried out for wetting the first end portion 203. Moreover, while themethod of wetting the second end portion 205 shown in FIGS. 3-4 isillustrated as being identical to the method of wetting the first endportion 203 shown in FIGS. 5-6, in further examples, different wettingtechniques may be applied to achieve the corresponding wetted endportion in further examples.

Soaking techniques will be initially described with reference to wettingthe second end portion 205 with the understanding that similar soakingtechniques may be carried out to wet the first end portion 203. Forexample, as shown in FIG. 2, a container 210 such as the illustrateddish may be filled with a quantity of liquid 213 to an initial level“L1”. The liquid can comprise water (e.g., purified water) althoughother liquids (e.g., glycerin, alcohol, etc.) may be used in furtherexamples. The second end portion 205 can then be soaked in the quantityof liquid to provide the second end portion as a wetted end portion.During an example soaking procedure, the second end portion 205 may besubmerged within a quantity of the liquid 213, wherein the liquid 213may then be drawn up by capillary forces to a depth against the force ofgravity. As shown in FIG. 4, the liquid may be effectively drawn up bythe capillary forces to a final wetted depth “D2” from the second endface 104.

As mentioned previously, example methods may carry out wetting of thefirst and/or second end portion to a final wetted depth that is within apredetermined range of acceptable depths. Indeed, in some examples,wetting can be carried out to a depth of at least about 5%, such as atleast about 20%, such as at least about 30%, such as at least about 40%of the length of the honeycomb filter. In some examples thepredetermined range can be from about 5% to about 10%, such as fromabout 10% to about 20%, such as from about 20% to about 30%, such asfrom about 30% to about 40% of the length of the honeycomb filter.

Various soaking techniques may be carried out to achieve the desiredfinal wetted depth. For example, as shown in FIG. 2, the quantity ofliquid 213 in the container 210 may be predetermined such that the stepof soaking draws the entire predetermined quantity of liquid into thewetted end portion. The quantity of liquid can be preselected to achievethe desired final wetted depth “D2”. For example, the quantity of liquidmay be determined based on prior soaking procedures to determine theextent that the liquid is drawn by capillary action into the end portionof the honeycomb filter. In one particular example, the predeterminedquantity of liquid may be calculated to achieve wetting of the secondend portion to a predetermined final wetted depth “D2”. In analternative procedure, the second end portion may be soaked apredetermined period of time that is known or calculated to result inthe desired final wetted depth “D2”.

The final wetted depth may also be obtained by dipping of the endportion within a quantity of liquid. For example, the second end portion205 may be dipped briefly in a quantity of liquid 213 to a depthapproximating the final wetted depth “D2”. The honeycomb filter 100 maythen be removed from the vicinity of the container 210 wherein excessliquid clinging to the dipped surfaces of the honeycomb filter 100 maybe absorbed into the walls to achieve the final wetted depth “D2”.

FIG. 6 demonstrates an example where both the first end portion 203 andthe second end portion 205 are each wetted to corresponding final wetteddepths D4 and D2, thereby leaving an unwetted intermediate portion 201.As mentioned previously, the wetted first end portion 203 helps reduceair flow through the wetted porous walls while still permitting fog toflow through any defect 209 in the first end portion 203. Likewise, thewetted second end portion 205 helps reduce air flow through the wettedporous walls while still permitting fog to flow through any defect 211in the second end portion 205. As such, the pressure differential withinthe intermediate portion 201 is increased to help identify any of thedefects 207 within the unwetted intermediate portion 201.

The method can further include the steps of flowing a fog with moisturedroplets into the honeycomb network of channels at the first end portionof the honeycomb filter and then monitoring the second end portion ofthe honeycomb filter for moisture droplets of the fog exiting thehoneycomb network of channels. The step of flowing the fog andmonitoring the second end portion can be carried out in a variety ofways, for example, with a testing apparatus.

Various testing apparatus may be provided in accordance with aspects ofthe disclosure. For example, FIG. 7 illustrates just one example of atest apparatus 701 being used to test the honeycomb filter 100 withwetted ends shown in FIG. 6. The test apparatus 701 is designed todetect defects in the interconnecting porous walls 106 and/or the plugs112 at one end of the each of the channels 108, 110. As mentionedpreviously, such defects are desirable to locate and address since theymay otherwise affect the performance of the honeycomb filter 100. Forexample, the porous walls 106 may include defects, such as cracks orholes, that allow relatively unrestricted flow between adjacent cells,thereby short circuiting the filtering process of the porous walls andthereby adversely affecting filtration efficiency and/or filtrationintegrity. Still further, defects may occur in the plugs 112 as holes orcracks within the plug and/or between the plug and the porous walls 106.In addition, plug defects may result from missing plugs or plugs thatonly partially fill the end of the channel. As such, the example testapparatus 701 may be provided to allow defects in the honeycomb filter100 to be readily detected.

As shown, the tests apparatus 701 can include a particulate source 703which operates to supply a flow of fog (as indicated by arrows “705”)which comprises gas with particulates suspended therein. The fog isprovided to an inlet end face 102 of the honeycomb filter 100. Theparticulates of the fog flow pass into the inlet cell channels 108 andthrough the porous walls 106 and/or plugs 112 of the honeycomb filter100 and, if not trapped by the porous walls, portions of the fog mayexit out through the outlet end face 104. Immediately upon exiting theoutlet end face 104, the fog can pass through a permeable member 707,such as a screen mounted adjacent to, and preferably engaged in directcontact with, the outlet end face 104. After exiting the permeablemember 707, the particulates of the fog may be illuminated by a plane oflight 709 projected in the vicinity of the permeable member 707. In oneexample, the plane of light 709 may be parallel to a plane of thepermeable member 707 and spaced a slight distance above. Defects in theplugs 112 and/or porous walls 106 may then be reliably detected in thehoneycomb filter 100 by inspection of the interference between theparticulates and the plane of light 709.

In one example, an image indicative of the locations of defective cellsis generated, for example by recording an image with an imager 711, suchas a camera. The image corresponding to the defective cell locations maybe stored in memory in a computer 713 and/or may also be displayed on avideo monitor 715. Defects in the porous walls 106 and/or plugs 112 showthemselves as bright spots in the image above the honeycomb filter 100,i.e., at the intersection with the plane of light 709. Accordingly,their location may be easily correlated with a cell defect location onthe honeycomb filter 100. In particular, before laying the permeablemember 707 on top of the honeycomb filter 100, a previous image may berecorded of the outlet end face 104, thereby capturing an image of thehoneycomb cell structure, i.e., the location in coordinate space (alongthe plane of the outlet end face 104) of the peripheral outline and therespective locations of the cells and plugs on the outlet end face 104.This image may then be correlated with the other image illustrating thebright spots to assign various cells as including defects.

The particulates can comprise liquid particles, such as fine liquidparticles. In operation, the particulates may be formed in a chamber 717by a particle generator 719 of the particulate source 703. Theparticulates may be generated by nebulizing, atomizing or otherwisespraying liquid through a nozzle. As mentioned previously, the liquidmay be water (e.g., purified water), a water-based solution, and/or aglycol-based solution that is provided at a fog. While water or otherliquid may be used, in alternative examples, smoke or other finesuspended particulate matter may be used in accordance with aspects ofthe disclosure. The particulates may be housed in a housing 721 andprovided under pressure through a flow path, which may be optionallydefined by a pipe 723 positioned between the particulate source 703 andthe inlet end face 102 of the honeycomb filter 100. The pipe 723, ifprovided, may include an optional round cross-section although othercross-sectional shapes are possible such as triangular, rectangular(e.g., square), or other polygonal shape or may comprise an ellipticalor other curvilinear shape. In one example, the pipe 723, if providedmay be axially aligned with the honeycomb filter 100. Further,preferably the inner dimension, D, (e.g., diameter) of the pipe 723 atthe point where the particulate laden gas is provided to the inlet endface 102 (near the pipe's upper end) is larger than a maximum transverseouter dimension, d, of the honeycomb filter 100. This feature improvesthe uniformity of the flow velocity profile, by reducing the effect ofboundary layer flow on the flow distribution of the gas, provided acrossthe inlet end face 102. The provision of pressure, preferably at greaterthan 30 Pa (relative pressure between the inlet and ambient), isachieved by a fan 725 forcing air into the housing 721. In someembodiments, the pressure is between 30 and 70 Pa. A perforatedpartition 727 may be employed to minimize variations in pressure withinthe chamber 717.

Upon passing through the honeycomb filter 100, the particulatescontained in the gas flow pass through the permeable member 707. Thepermeable member 707 may be a screen, mesh, cloth, or perforated sheet.In one example, the permeable member 707 may be manufactured from afilamentary material, such as a woven or interlaced strand or wirematerial having multiple oriented strands. The strands may be orientedin a generally perpendicular manner; although this orientation is notrequired. For example, the member may be woven in chain linkorientation. In one example, wire cloth or mesh may be provided. Inanother example, metal wire cloth, such as stainless steel wire cloth,may also be used. The permeable member 707 preferably includes a meshdensity of greater than about 50 threads/inch, or even greater than 125threads/inch, and in some embodiments greater than about 250threads/inch. The diameter of the wire strands (filaments) in the meshor cloth may be less than about 0.005 inch (less than about 127microns), less than about 0.004 inch (less than about 102 microns), oreven less than about 0.002 inch (less than about 51 microns). In oneexemplary embodiment, the permeable member 707 includes wire meshdensity of greater than about 50 threads/inch, and a diameter of thewire is preferably less than about 0.004 inch (less than about 102microns). A fine screen having a 30 micron diameter and 325 threads/inchmay be provided. Permeable member 707 may also be chiffon or other knitcloth or mesh, or any other finely knitted, interlaced, or grid formingcloth material.

The permeable member 707 may be disposed adjacent to or in contact withthe outlet end face 104 of the honeycomb filter 100. As shown, an imageenhancement apparatus 729 may be provided with a frame 731 (e.g., anannular frame) configured to mount the permeable member 707 within acentral area defined by the frame 731. In one example, the permeablemember 707 may be stretched across the frame 731 so as to construct aplane, and preferably held by the frame, such as an adjustable diameterring frame.

In some examples, the permeable member 707 may include ananti-reflective surface. If provided, the anti-reflective surface may besubstantially absorbing of the light of the wavelength of the lightsource used for illumination. For example, the screen may be coloredwith a dark surface coloring, for example flat black or matte black orother colors that are absorbing, such as brown or navy blue. Embodimentsmay include a coating, such as a black oxide coating. The dark coloringhelps improve the signal-to-noise level between the signal and lower thebackground noise.

In one example, an illumination apparatus 733 is provided with a lightsource 735 for generating the plane of light 709 adjacent to and spacedfrom the outlet end face 104 of the honeycomb filter 100. The plane oflight 709 may also be spaced from the plane of the permeable member 707.One example of a light source 735 is configured to generate the plane oflight 709 as a red or green laser although other laser types or lightdevices may be used in further examples. The light source 735 may beconfigured to cooperate with optical elements, such as a rotatingfaceted mirror 737, to convert the light beam to the planar sheet oflight 709. The illumination apparatus 733 is configured to produce theplane of light 709 that may be generally parallel to the outlet end face104 and a plane of the permeable member 707. The plane of light 709 canalso be large enough to fully span across the end face 104 of thehoneycomb filter 100.

In further examples, it may be desirable to control the spread of theplane of light 709. In such examples, a slot 739 may be formed inuprights 741 through which the plane of light 709 extends such that awell-defined plane of light 709 is projected above the outlet end face104. The width of the slot 739 defined by the upright 741 can beselected to control spread of the plane of light 709. The uprights 741can also control eddy current and otherwise minimize air flowdisturbances around the honeycomb filter 100. Preferably, the distancebetween the plane of light 709 and the outlet end face 104 is such thatthe particulates emerging from the outlet end face 104 still havesufficient momentum to intersect the plane of light 709. Thus, plane oflight 709 may be designed to be as close as possible to the outlet endface 104 and permeable member 707 without interfering with the outletend face 104. In one embodiment, the distance between the plane of light709 and the permeable member 707 is in a range from 1/16 in. (1.6 mm) to½ in. (12.7 mm). In further examples, other light sources may beprovided such as ultraviolet light or infrared lasers to produce theplane of light.

After particulates emerge from the permeable member 707, theillumination apparatus 733 is configured to illuminate the particulatesin the flow and an imager 711 may be configured to capture an image ofthe X-Y position of particles illuminated (the bright spots) due tointerference with the plane of light 709 as the particles emerge fromthe outlet end face 104 of the honeycomb filter 100. The imager 711 mayrecord an image (e.g., digital image), of the interference pattern ofthe flow emerging from the permeable member 707. The image may then beprocessed to detect the presence of, and location of, defectivecells/plugs, such that corrective action (e.g., repairing, discarding,etc.) may be taken. Image processing may include a pixel-by-pixelcomparison of the image against an intensity threshold. The processmethodology may indicate a defect when the intensity is above apre-selected threshold.

The imager 711, such as a camera or camcorder, may be positioned abovethe outlet end face 104 of the honeycomb filter 100 to capture an imageof any illuminated particles flowing out of the outlet end face 104. Inparticular, the areas where defects are indicated show up as brightspots in the image. In the case of a single defect, the defect isidentified as a relatively bright spot located above the cell that hasparticulate within the gas stream due to the defect within the honeycombfilter 100. As such, an analysis of the image can help immediatelylocate the X-Y position of the defect along the outlet end face 104. Theimager 711 may further include an optical system, such as lenses, forfocusing on the illuminated region. The imager 711 may include or beattached to an internal processor or computer 713 which processesinformation collected by the imager into image files and stores theimage files in memory. The processor may support various types of imagefile formats, such as TIFF and JPEG or other file formats. The computer713 may include a video monitor 715 and other peripheral devicesnecessary for interacting with the system, such as a keyboard and mouse(not shown). The image files from the imager 711 can be transferred tothe computer 713 further processing. The image files may also bedisplayed on the video monitor 715.

Cells in the honeycomb filter 100 having defects would discharge moreparticulates and larger particulates than cells not having defects. Thesize of the spots can provide an indication of the size of the defectsin the honeycomb filter 100. If the image appears uniform, then the testwould indicate no defects in the honeycomb filter 100. Advantageously,the use of the permeable member 707 can reduce the overall backgroundobjects that may confuse the image, thereby increasing thesignal-to-noise ratio such that the bright spots associated with defectsmay be more readily detected.

Example methods of testing a honeycomb filter 100 will now be described.Initially, as shown in FIG. 1, the honeycomb filter 100 may be providedwith the intermediate portion 201 disposed between the first end portion203 and the second end portion 205 along the length “L” of the honeycombfilter 100. The honeycomb filter 100 includes the honeycomb network ofchannels 107 defined by the plurality of intersecting porous walls 106.The honeycomb network of channels 107 extend along the length “L” of thehoneycomb filter 100 between the first end portion 203 and the secondend portion 205. In one example a first end portion and/or a second endportion of the honeycomb filter may be wetted such that the wetted endportion has a higher degree of wetness than the intermediate portion. Inone example, the method includes the step of wetting the first endportion 203 to a depth of from about 5% to about 40% of the length “L”of the honeycomb filter 100 to provide a first wetted end portion havinga higher degree of wetness than the intermediate portion. In addition oralternatively, in another example, the method includes the step ofwetting the second end portion to a depth of from about 5% to about 40%of the length of the honeycomb filter to provide a second wetted endportion having a higher degree of wetness than the intermediate portion.As discussed above, the step of wetting can be carried out with aliquid, such as water although other liquids may be used in furtherexamples. Moreover, as discussed above, the method of wetting can becarried out by exposing the ends to vapor, dipping in a quantity ofwater, soaking in water and/or other wetting techniques.

As shown in FIG. 8, the wetted end portions 203 and 205 can help plugcorresponding pores within the porous walls of the end portions whilestill permitting flow of fog through defects 209, 211 located within thecorresponding end portions 203 and 205. At the same time, the pressuredifferential is increased within the intermediate portion 201, therebyallowing increased flow of fog through the defect 207 within theintermediate portion 201. As such, analysis of any defects locatedwithin the intermediate portion 201 may be carried out in a moreeffective manner.

The method can include flowing a fog 801 with moisture droplets into thehoneycomb network of channels at the first end portion 203 of thehoneycomb filter 100. For example, referring to FIG. 8, the testapparatus may be used to flow fog 801 with moisture droplets into thehoneycomb network of channels. Moreover, the method can include the stepof monitoring the second end portion 205 of the honeycomb filter formoisture droplets of the fog exiting the honeycomb network of channels.In one example, the test apparatus 701 may be used to monitor the secondend portion 205, for example, by illuminating moisture droplets of thefog exiting the honeycomb network of channels.

As such, referring to FIG. 8, wetting of the end portions 203, 205 canat least partially (e.g., completely) plug the pores within thecorresponding end portions. As such, increased pressure differential maybe achieved within the intermediate portion 201 to allow enhanceddetection of any defects 207 within the intermediate portion. At thesame time, wetting the end portions may be insufficient to plug thedefects 209 and 211 within the corresponding end portions. As such,wetting the end portions can increase the sensitivity of the testingapparatus, thereby allowing enhanced detection of the defects 207 withinthe intermediate portion while also permitting detection of defects 209,211 within the end portions.

An experiment was conducted on a honeycomb filter where 9 artificiallycreated defects in the filter were created. Three defects wheregenerated in each of the first end portion, the second end portion andthe intermediate portion of the honeycomb filter. A nebulizer test wasperformed on the dry filter wherein fog was passed through the first endof the filter while the second end of the filter was monitored. Thedisplayed pixel size of each defect was recorded. Then, both ends werewetted and the same nebulizing procedure was carried out wherein thepixel size of each defect was noted again. The test noted that the pixelsize of all three defects in each of the first end portion, second endportion and intermediate portion of the honeycomb filter was greaterwith the honeycomb filter having wetted end portions when compared tothe honeycomb filter having dry end portions. The testing found anincrease in detectability of 1.6× of defects within the first endportion, an increase in detectability of 5.8× of defects within theintermediate portion, and an increase in detectability of 1.8× of thedefects within the second end portion.

Defects within outer peripheral channels may also be more difficult todetect than defects located within interior channels. As such, inaccordance with one aspect of the disclosure, an outer peripheralsurface 109 of the honeycomb filter 100 may be wetted to enhance flow offog through outer peripheral channels of the honeycomb network ofchannels.

FIGS. 9 and 10 illustrate just one example of wetting the outerperipheral surface 109, such as an outer peripheral skin of thehoneycomb filter 100. For example, the central axis 901 may be orientedat an angle relative to vertical and can even be located horizontal asshown in FIG. 9. As shown in FIGS. 9 and 10, the one or more rollers 903may rotate to allow the honeycomb filter 100 to rotate along direction1001 about the central axis 901. During rotation, a spraying arm 905 mayextend along the length “L” of the honeycomb filter 100. As such, as thehoneycomb filter 100 rotates about the central axis 901, a series ofspray nozzles 907 disposed along the length “L” of the honeycomb filter100 allow the liquid to coat the outside of the outer peripheral surface109. The liquid, such as water (e.g., purified water), a water-basedsolution, a glycol-based solution or other liquid, may then soak intothe outer peripheral surface 109.

FIGS. 7 and 10 illustrate another example of wetting the outerperipheral surface 109. As shown in broken lines in FIG. 7, thehoneycomb filter 100 may be oriented with the central axis 901 of thehoneycomb filter 100 being substantially vertical. A peripheral sprayring 750 may be provided in communication with a pressured water supply752. The honeycomb filter may be moved up in a direction 751 of the axisthrough a central passage of the peripheral spray ring 750. A somewhatschematic illustration of the peripheral spray ring 750 is illustratedin broken lines in FIG. 10 as an alternative to the illustrated sprayingarm 905. As shown, the spray ring include a central passage 1003 with aplurality of nozzles 1005 oriented to spray liquid towards an interiorof the peripheral spray ring 750. As such, turning back to FIG. 7, thehoneycomb filter 100 may be moved upward in direction 751 through thecentral passage 1003 of the peripheral spray ring as the honeycombfilter 100 is in the process of being mounted in position for testing bythe test apparatus 701.

Once the outer peripheral surface 109 is wetted, the outer peripheralsurface 109 (e.g., the provided by the illustrated outer peripheralskin) is loaded with liquid. As such, particulate within the fog 1101 isnot as likely to be absorbed by the outer peripheral surface 109 sincethe outer peripheral surface 109 is already loaded with a quantity ofliquid. Rather, the particulate within the fog 1101 is more likely toreach the defect 1104 located in an outer peripheral wall 1105 of thenetwork of channels 107. As such, as shown, the particulate path 1107can eventually leave the outlet end face 104 for detection by the testapparatus 701.

As such, methods of testing a honeycomb filter 100 are provided. Themethods include the step of providing the honeycomb filter 100 includingthe first end portion 203 and the second end portion 205 along the axis901 of the honeycomb filter 100. The honeycomb filter 100 can includethe network of channels 107 defined by the plurality of intersectingwalls 106. The honeycomb network of channels 107 extend along the axis901 of the honeycomb filter 100 between the first end portion 203 andthe second end portion 205. The honeycomb filter 100 is provided with anouter peripheral surface 109 circumscribing the honeycomb network ofchannels 107 and extending between the first end portion 203 and thesecond end portion 205. As shown, in one example, the honeycomb filter100 can include an optional outer peripheral skin 1103 that provides theouter peripheral surface 109.

The outer peripheral skin 1103 may be provided in various ways. Forexample, the outer peripheral skin 1103 may be simultaneously formedwith the plurality of intersecting walls 106. For instance, theintersecting walls 106 may be coextruded with the outer peripheral skin1103 from a batch of ceramic and/or ceramic-forming material.Alternatively, the intersecting walls 106 may be extruded and then theouter peripheral skin 1103 may be subsequently applied. In one example,the intersecting walls 106 are formed. The outer periphery of theintersecting walls 106 may be optionally machined and then the outerperipheral skin may be applied, for example, by way of a doctor blade orother application technique.

Testing can then proceed by wetting the outer peripheral surface 109,for example, spraying techniques described with respect to FIG. 10above. In one example, the spraying techniques include spraying with aliquid, for example glycerin, alcohol, water (e.g., purified water). Forinstance, referring to FIG. 7, the honeycomb filter 100 may be loadedinto an interior area of the particulate source 703. The method can thentranslate the honeycomb filter 100 in a direction of the axis of thehoneycomb filter through the central passage of a peripheral spray ring750 while the spray ring wets the outer peripheral surface 109 of thehoneycomb filter 100.

Wetting the outer peripheral surface 109, for example, can load theouter peripheral skin 1103 with moisture. Next, the method can proceedby flowing a fog with moisture droplets into the honeycomb network ofchannels at the first end portion 203 of the honeycomb filter. Afterbeing wetted, for example, by the peripheral spray ring 750, thehoneycomb filter can be loaded into position as shown in FIG. 7. Thenthe second end portion 205 of the honeycomb filter can be monitored formoisture droplets of the fog exiting the honeycomb network of channels.As the outer peripheral surface of the honeycomb filter was wetted, fogwithin the outer peripheral channels will not have the tendency of beingabsorbed to the extent it would if the outer peripheral skin was testedwhen initially dry. As such, wetting the outer peripheral surface 109prior to beginning the procedure of monitoring the fog exiting thesecond end portion of the honeycomb substrate can enhance the flow offog through the outer peripheral channels and thereby allow defectsassociated with the outer peripheral walls of the intersecting walls 106to be more readily identified.

FIGS. 12 and 13 represent test results illustrating the effectiveness ofsaturating the outer peripheral skin of a honeycomb filter prior toconducting a testing procedure with a nebulizer configuration. BothFIGS. 12 and 13 used a filter with two known flaws (i.e., defects)provided in the perimeter of the part. The two flaws are represented bytwo different cross-sectional appearances referenced in the legend ofthe graphs as “F1” (i.e., flaw 1) and “F2” (flaw 2) The vertical axis(i.e., Y-axis) in the graphs are the pixel size of the observed flaw.The regions “A” in the horizontal (i.e., X-axis) of FIG. 12 indicatestest results for a dry honeycomb filter while the regions “B” indicatetest results for a honeycomb filter wherein the outer peripheral surfacewas wetted prior to the test procedure. Test results were taken after 10seconds, 20 seconds and 30 seconds as indicated by “10”, “20”, and “30”along the horizontal (i.e., X-axis) of FIG. 12.

Referring to region “A” of FIG. 12 after 10 seconds of testing, neitherof the flaws “F1” or “F2” the dry honeycomb filter was identified.Referring to region “B” of FIG. 12 after 10 seconds of testing, thefirst flaw “F1” was identified but the second flaw “F2” was not yetidentified.

Referring to region “A” of FIG. 12 after 20 seconds of testing, only thefirst flaw “F1” of the dry honeycomb filter was identified. However, asindicated by region “B” after 20 seconds of testing, both flaws “F1” and“F2” were identified and the pixel size associated with the first flaw“F1” was significantly larger than the pixel size of the same flaw after10 seconds.

Referring to region “A” of FIG. 12 after 30 seconds of testing, only thefirst flaw “F1” of the dry honeycomb filter was identified (althoughmore pronounced) while the second flaw “F2” was not identified. Incontrast, as indicated by region “B” after 30 seconds of testing, bothflaws “F1” and “F2” were again identified and the pixel size associatedwith both flaws were again greater than the corresponding pixel size ofthe flaws after 20 seconds of testing.

As such, without wetting the outer peripheral skin of the honeycombfilter, the second flaw “F2” would never have been detected. Incontrast, wetting the outer peripheral surface resulted in detection ofmore flaws that were more visible when compared to dry honeycombfilters. As shown, increased time of testing can result in greaterchance of detection and more visible flaws. In some examples of thedisclosure, testing can include wetting the outer peripheral skin of thehoneycomb filter and then testing for flaws with a nebulizer or otherfog generator for greater than or equal to 10 seconds, for examplegreater than or equal to 20 seconds, for example greater than or equalto 30 seconds, for example greater than or equal to 40 seconds.

FIG. 13 illustrates the repeatability (displayed by the error bars) forhoneycomb filters with a wetted outer peripheral skin after 30 seconds.The sample size was five runs and one standard deviation is shown by theerror bars. As indicated, wetting the outer peripheral skin prior totesting was effective in detecting both flaws “F1” and “F2” at a pixelsize of greater than 45.

In addition or in alternative to wetting the outer peripheral surface109, a flow of fog through inner peripheral channels may be inhibited,such as prevented, to enhance the flow of fog through the outerperipheral channels. For example, the method can include the step ofobstructing a flow of fog through the inner peripheral channels at thefirst end portion 203 of the honeycomb filter 100. In addition or in thealternative, the method can include the step of obstructing a flow offog through the inner peripheral channels at the second end portion 205of the honeycomb filter 100.

FIGS. 14-16 illustrate apparatus and methods of testing by obstructing aflow of fog through the inner peripheral channels at the second endportion 205. In one example, the apparatus for testing the honeycombfilter can comprise a flow diverter configured to enhance the flow offog through the outer peripheral channels 1503, 1505 while reducing, forexample preventing, the flow of fog through the inner peripheralchannels 1507.

In one example, the flow diverter can substantially completely preventthe flow of fog through the inner peripheral channels 1507. FIGS. 14-15illustrate just one example of a blocking apparatus 1401 that may beprovided with a blocking member 1403 configured to engage a centralportion 1501 of the second end portion 205 of the honeycomb filter 100to enhance the flow of fog from the fog generator through the outerperipheral channels 1503. The blocking member 1403 can comprise a plateconstructed of plastic, metal or other material configurationsubstantially impermeable to gas flow. As shown in FIG. 15, in just oneexample, the blocking member 1403 can include a peripheral seal 1509configured to seal against the honeycomb filter 100. As furtherillustrated, the apparatus may also include a support mesh 1405supporting the blocking member 1403 within a central portion of thesupport mesh 1405. For example, a peripheral frame 1407 may be providedto help mount the support mesh 1405, for example, in a substantiallyplanar orientation. As shown in FIG. 15, the blocking member 1403 may bemounted to one side of the support mesh 1405 while the peripheral seal1509 is mounted to the other side of the blocking member 1403. Thesupport mesh 1405 is gas permeable to allow free movement of fog or gasassociated with the fog to pass through the support mesh and therebyfreely exit the second end portion 205 of the honeycomb filter 100. Atthe same time, the gas permeable mesh still provides sufficient supportto allow sufficient engagement of the peripheral seal 1509 to inhibit,such as prevent, movement of gas through the inner peripheral channels1507.

In further examples, the blocking member 1403 is configured to pivotbetween a blocking orientation (see FIG. 15) and a retracted orientation(see FIG. 16). For example, as shown in FIGS. 14 and 15, the apparatuscan include a pivot arm 1409 configured to pivot about a pivot axis 1411between the closed orientation and the open orientation. As shown, inFIG. 14, in the closed orientation, the flow of fog through the innerperipheral channels 1507 is obstructed to enhance the flow of fogthrough the outer peripheral channels 1503, 1505. As such, a defect 1104in the outer peripheral channel is more likely to be detected at thesecond end portion 205, for example, by the test apparatus 701 shown inFIG. 7. However, as the flow of fog is blocked through the innerperipheral channels 1507, inner defects 1511 associated with the innerchannels cannot be detected by the test apparatus 701.

To detect the inner defects 1511, the blocking member 1403 can also bepivoted to an open orientation, as shown in FIG. 16, wherein fog is freeto flow in all of the channels. As shown by arrows 1601, fog may beabsorbed by the dry outer peripheral skin 1103 prior to reaching thedefect 1104. As such, fog may not short circuit through the defect 1104in sufficient quantities to be detected at the second end portion.However, as the central channels are not adjacent the outer peripheralskin 1103, absorption issues are not a concern. As such, as shown inFIG. 16, the fog entering the first end portion 203 may pass through thedefect 1511 to allow the defect to be observed by the test apparatus 701at the second end portion of the honeycomb filter 100.

As such, the test apparatus 701 can include a blocking apparatus 1401that allows monitoring for defects associated with the inner peripheralchannels 1507 when the blocking apparatus is oriented in the openorientation (see FIG. 16). The blocking apparatus 1401 can also allowfor monitoring of defects associated with the outer peripheral channels1505, 1507 when the blocking apparatus 1401 is oriented in the closedorientation shown in FIG. 15.

FIGS. 17-18 illustrate another example wherein the previously-describedblocking apparatus 1401 that may be provided with the blocking member1403 configured to engage a central portion 1701 of the first endportion 203 of the honeycomb filter 100 to enhance the flow of fog fromthe fog generator through the outer peripheral channels 1503, 1505.

The blocking member 1403 is configured to pivot between a blockingorientation (see FIG. 17) and a retracted orientation (see FIG. 18). Asshown, in FIG. 17, in the closed orientation, the flow of fog throughthe inner peripheral channels 1703 is obstructed to enhance the flow offog through the outer peripheral channels 1705, 1707. As such, a defect1104 in the outer peripheral channel is more likely to be detected atthe second end portion 205, for example, by the test apparatus 701 shownin FIG. 7. However, as the flow of fog is blocked through the innerperipheral channels 1703, inner defects 1511 associated with the innerchannels cannot be detected by the test apparatus 701.

To detect the inner defects 1511, the blocking member 1403 can also bepivoted to an open orientation, as shown in FIG. 18, wherein fog is freeto flow in all of the channels. As shown by arrows 1601, fog may beabsorbed by the dry outer peripheral skin 1103 prior to reaching thedefect 1104. As such, fog may not short circuit through the defect 1104in sufficient quantities to be detected at the second end portion 205.However, as the central channels are not adjacent the outer peripheralskin 1103, absorption issues are not a concern. As such, as shown inFIG. 18, the fog entering the first end portion 203 may pass through thedefect 1511 to allow the defect to be observed by the test apparatus 701at the second end portion of the honeycomb filter 100.

As such, the test apparatus 701 can include a blocking apparatus 1401that allows monitoring for defects associated with the inner peripheralchannels 1703 when the blocking apparatus is oriented in the openorientation (see FIG. 18). The blocking apparatus 1401 can also allowfor monitoring of defects associated with the outer peripheral channels1705, 1707 when the blocking apparatus 1401 is oriented in the closedorientation shown in FIG. 17.

FIGS. 19 and 20 illustrate another example of a blocking apparatus 1901that may be provided with a blocking member 1903 configured to engage acentral portion 1701 of the first end portion 203 of the honeycombfilter 100 to enhance the flow of fog from the fog generator through theouter peripheral channels 1705, 1707. The blocking apparatus 1901 cancomprise an piston 1905 extendable by a linear actuator 1906 configuredto be extended to the closed orientation shown in FIG. 19 or retractedto the open orientation shown in FIG. 20. In the closed orientationshown in FIG. 19, defects in the outer peripheral channels 1705, 1707may be detected in a similar manner as discussed with respect to FIG. 17above. Likewise, in the open orientation shown in FIG. 20, defects inthe inner peripheral channels 1703 can be detected in a similar manneras discussed with respect to FIG. 18 above. While the blocking apparatus1901 is shown to engage the central portion 1701 of the first endportion 203, in further examples, a similar blocking apparatus may beoriented to engage a central portion of the second end portion 205.

FIGS. 21 and 22 illustrate another example of a blocking apparatus 2101that may be provided with a blocking member configured to engage acentral portion 1701 of the first end portion 203 of the honeycombfilter 100 to enhance the flow of fog from the fog generator through theouter peripheral channels 1705, 1707. The blocking apparatus 2101 cancomprise an inflatable bladder 2103 that may be inflated to be extendedto a closed orientation shown in FIG. 21 or deflated to the openorientation shown in FIG. 22. In the closed orientation shown in FIG.21, defects in the outer peripheral channels 1705, 1707 may be detectedin a similar manner as discussed with respect to FIG. 17 above.Likewise, in the open orientation shown in FIG. 22, defects in the innerperipheral channels 1703 can be detected in a similar manner asdiscussed with respect to FIG. 18 above. While the blocking apparatus2101 is shown to engage the central portion 1701 of the first endportion 203, in further examples, a similar blocking apparatus may beoriented to engage a central portion of the second end portion 205.

FIG. 23 illustrates an example of a flow diverter 2301 that does notnecessarily engage the honeycomb filter but may engage in furtherexamples. Indeed, as shown in solid lines, the flow diverter 2301 maycome close to the first end portion 203 of the honeycomb filter 100without engaging. The flow diverter 2301 may comprise a solid conicalmember wherein fog flow may be diverted about the periphery of the flowdiverter 2301 such that a greater quantity of fog is directed throughthe outer peripheral channels 1705, 1707 such that defects in the outerperipheral channels 1705, 1707 may be detected in a similar manner asdiscussed with respect to FIG. 17 above. Likewise, in the openorientation shown in dashed lines, defects in the inner peripheralchannels 1703 can be detected in a similar manner as discussed withrespect to FIG. 18 above.

Methods of testing the honeycomb filter 100 can therefore comprise thestep of flowing fog with moisture droplets into the honeycomb network ofchannels at the first end portion 203 of the honeycomb filter 100. Themethod can further include the step of monitoring the second end portion205 of the honeycomb filter 100 for moisture droplets of the fog exitingthe honeycomb network of channels. The method can also include the stepof obstructing a flow of fog through inner peripheral channels toenhance the flow of fog through the outer peripheral channels of thehoneycomb network of channels.

As shown for example in FIGS. 17, 19 and 21, the method can includeobstructing a flow of fog through the inner peripheral channels 1703 atthe first end portion 203 of the honeycomb filter 100. As shown in FIG.15, the method can also include the step of obstructing a flow of fogthrough the inner peripheral channels 1507 at the second end portion 205of the honeycomb filter 100.

In some examples, the step of monitoring can occur prior to the step ofobstructing. For example, as shown in FIGS. 16, 18, 20 and 22,monitoring may be initially carried out to help determine defects withinthe inner peripheral channels. In further examples, the step ofmonitoring can occur after the step of obstructing. For example, asshown in FIGS. 15, 17, 19, and 21, monitoring may be initially carriedout to help determine defects within the outer peripheral channels. Instill further examples, the monitoring may occur before and after thestep of obstructing. For example, as shown in FIGS. 16, 18, 20 and 22,monitoring may be initially carried out to help determine defects withinthe inner peripheral channels. As shown in FIGS. 15, 17, 19, and 21,monitoring may be then be subsequently carried out to help determinedefects within the outer peripheral channels. In still further examples,monitoring may be initially carried out to determine defects in theouter peripheral channels and then subsequently carried out to determinedefects in the inner peripheral channels.

Methods of testing a honeycomb filter with the fog generator, such as anebulizer can be carried out under various processing parameters to helpincrease the efficiency and capability to identify defects within thehoneycomb filter. For example, modeling indicates that temperaturesignificantly affects the particle size distribution of the fog due towater droplet evaporation and condensation which affects the detectionquality of the nebulizer setup. In one example, the honeycomb filters100 may be maintained at an average temperature within a range of from10° C. to about 30° C., for example from about 10° C. to about 25° C.,for example, from about 20° C. to about 23° C. Such temperature rangescan allow maintenance of the droplet size distribution which can helpcontrol the process accuracy. Air humidity can also affect quality ofthe nebulizer set up. In one example, methods include flowing a fog withmoisture droplets into the honeycomb network of channels at the firstend portion 203 of the honeycomb filter 100 wherein the fog has arelative humidity of at least 80%. Providing appropriate maintenance ofthe honeycomb filter temperature within the ranges above together withthe fog including a relative humidity of at least 80% can help increasethe effectiveness of the test procedure. As such, the method can furtherinclude the step of effectively monitoring the second end portion 205 ofthe honeycomb filter 100 for moisture droplets of the fog exiting thehoneycomb network of channels.

In further examples the temperature of the fog can also be controlled tohelp enhance performance of the testing procedure. For instance, in oneexample, the method includes the step of flowing fog with a temperaturewithin a range of from about 10° C. to about 30° C., for example fromabout 10° C. to about 25° C., for example from about 23° C. to about 25°C.

In some testing environments, it is recognized that surroundingenvironmental ambient temperatures can swing widely throughout the year,resulting in variation in time duration and results. Variation increasesover 25° C. can make fog generation difficult. In some examples, thetesting apparatus may be placed in a controlled environment to ensurethe temperature does not exceed 25° C. For example, a control room maybe provided with the testing apparatus, wherein the control room ismaintained at a temperature that does not exceed 25° C. while thetemperature outside of the control room may vary above the 25° C.threshold.

Still further, the moisture droplets of the fog can be controlled tohelp enhance the ability to identify defects in the filter. Based onunit filtration modeling data for a typical filter, as the droplet sizeof the fog becomes larger than 1 micron, it is more likely to befiltered out by the porous walls of an unflawed filter. On the otherhand, droplets smaller than 1 micron may be able to navigate through theporous walls and provide a false reading of a defect within the filter.As such, in some examples, there is a desire to provide fog withdroplets including a size of larger than 1 micron to allow the porouswalls to effectively filter out the droplets when there is no defectpresent. Still further, the larger the droplet size, the interruptionoccurs with the light being used to illuminate any droplets emergingfrom the second end portion 205 of the honeycomb filter 100. Indeed,larger droplets will appear as brighter spots on the images. Very largedroplet sizes may then have the benefit of being effectively filteredout by the porous walls while also being easily detected by imaging atthe second end portion 20 of the honeycomb filter 100.

However, there is an upper limit imposed due to inertia of the particlesflowing through the filter. As such, methods can provide fog withmoisture droplets having a mean droplet size of from about 1 micron toabout 25 microns, for example, from about 5 microns to about 25 microns,for example, from about 10 microns to about 15 microns. In someexamples, it is possible to use larger droplets at lower relativehumidity so that when the droplets flow, they will evaporate, therebyreducing the droplet size and increasing the humidity of the fog. Suchdroplet sizes are believed to be sufficient size for effectivefiltration by the porous walls without being so large that adverse flowconditions occur do to the inertia of the particles navigating throughthe defects in the walls of the honeycomb filter.

In still further examples, pressure differentials may be controlledbetween the first end portion and the second end portion to help provideadequate pressure drop to facilitate the testing procedure. In oneexample, the fog can have a pressure differential between the first endportion 203 and the second end portion 205 of the honeycomb filter 100of from about 32 Pa to about 37 Pa. Such pressure differentials may helpprovide a desired flow of fog through the honeycomb network of channels.In one example, the channels have a flow rate of from about 0.075 msecto about 0.1 msec.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the described embodimentswithout departing from the spirit and scope of the claimed invention.Thus, it is intended that the present claimed invention cover themodifications and variations of the embodiments described hereinprovided they come within the scope of the appended claims and theirequivalents.

What is claimed is:
 1. A method of testing a honeycomb filter comprisingthe steps of: (I) providing a honeycomb filter including an intermediateportion disposed between a first end portion and a second end portionalong a length of the honeycomb filter, the honeycomb filter includinghoneycomb network of channels defined by a plurality of intersectingporous walls, wherein the honeycomb network of channels extend along thelength of the honeycomb filter between the first end portion and thesecond end portion; (II) wetting at least one of the first end portionand the second end portion to provide at least one wetted end portion,wherein the wetted end portion has a higher degree of wetness than theintermediate portion; (III) flowing a fog with moisture droplets intothe honeycomb network of channels at the first end portion of thehoneycomb filter; and (IV) monitoring the second end portion of thehoneycomb filter for moisture droplets of the fog exiting the honeycombnetwork of channels.
 2. The method of claim 1, wherein step (II)includes wetting the at least one of the first end portion and thesecond end portion to a depth of at least about 5% of the length of thehoneycomb filter.
 3. The method of claim 1, wherein step (II) includeswetting the at least one of the first end portion and the second endportion to a depth of at least about 20% of the length of the honeycombfilter.
 4. The method of claim 1, wherein step (II) includes wetting theat least one of the first end portion and the second end portion to adepth of at least about 30% of the length of the honeycomb filter. 5.The method of claim 1, wherein step (II) includes wetting the at leastone of the first end portion and the second end portion to a depth ofless than about 40% of the length of the honeycomb filter.
 6. The methodof claim 1, wherein step (II) includes wetting the at least one of thefirst end portion and the second end portion with liquid.
 7. The methodof claim 6, wherein step (II) includes wetting the at least one of thefirst end portion and the second end portion with water as the liquid.8. The method of claim 1, wherein step (II) includes dipping at leastone of the first end portion and the second end portion in liquid toprovide the wetted end portion.
 9. The method of claim 8, wherein step(II) includes dipping the at least one of the first end portion and thesecond end portion in water as the liquid to provide the wetted endportion.
 10. The method of claim 1, wherein step (II) includes soakingat least one of the first end portion and the second end portion in aquantity of liquid to provide the wetted end portion.
 11. The method ofclaim 10, wherein step (II) includes soaking the at least one of thefirst end portion and the second end portion with a quantity of water asthe quantity of liquid to provide the wetted end portion.
 12. The methodof claim 10, wherein step (II) includes providing the quantity of liquidas a predetermined quantity of liquid in a container, and the step ofsoaking draws the entire predetermined quantity of liquid into thewetted end portion.
 13. The method of claim 12, wherein thepredetermined quantity of liquid is calculated to achieve wetting of theat least one of the first end portion and the second end portion to apredetermined depth.
 14. The method of claim 10, wherein step (II)includes soaking such that liquid is drawn by capillary forces to adepth against the force of gravity.
 15. The method of claim 1, whereinstep (II) includes wetting both the first end portion and the second endportion to provide the at least one wetted end portion as a first wettedend portion and a second wetted end portion.
 16. The method of claim 1,wherein step (IV) includes illuminating moisture droplets of the fogexiting the honeycomb network of channels.
 17. A method of testing ahoneycomb filter comprising the steps of: (I) providing a honeycombfilter including an intermediate portion disposed between a first endportion and a second end portion along a length of the honeycomb filter,the honeycomb filter including honeycomb network of channels defined bya plurality of intersecting porous walls, wherein the honeycomb networkof channels extend along the length of the honeycomb filter between thefirst end portion and the second end portion; (II) wetting the first endportion to a depth of from about 5% to about 40% of the length of thehoneycomb filter to provide a first wetted end portion having a higherdegree of wetness than the intermediate portion; (III) wetting thesecond end portion to a depth of from about 5% to about 40% of thelength of the honeycomb filter to provide a second wetted end portionhaving a higher degree of wetness than the intermediate portion; (IV)flowing a fog with moisture droplets into the honeycomb network ofchannels at the first end portion of the honeycomb filter; and (V)monitoring the second end portion of the honeycomb filter for moisturedroplets of the fog exiting the honeycomb network of channels.
 18. Themethod of claim 17, wherein at least one of step (II) and step (III)includes wetting at least one of the first end portion and the secondend portion with liquid.
 19. The method of claim 18, wherein at leastone of step (II) and step (III) includes wetting at least one of thefirst end portion and the second end portion with water as the liquid.20. The method of claim 17, wherein step (V) includes illuminatingmoisture droplets of the fog exiting the honeycomb network of channels.